text:
Does rain affect VFR criteria?
Does rain affect VFR criteria? In other words, if visibility is 1500m or more and you are in sight of the surface, but there is heavy rain, can you still fly VFR?
Here is an example of the conditions I'm asking about.

Was visibility really 1500m inside of that rain shower?

1500 metres of visibility is a lot worse than you might think! The visibility is definitely greater than 1500 metres in that video

@quietflyer I believe so. The focus of the camera was on the raindrops on the windshield, so it is hard to judge the visibility because everything further away than a couple of meters was blurred anyway.

@DeltaLima: In the video we can see a horizon, and tree outlines on the ground.  If visibility was really that low, wouldn't you not see a horizon?  (Or maybe that's just a nearby ridge or edge of a forest they're flying towards.)

@PeterCordes don't get me wrong, I think the visibility was well over 1500 m. It is the out-of-focus camera that may give the impression that visibility was bad. OTOH, in heavy  rain ,cameras give sometimes a better visibility that what you see out of the window.

@DeltaLima: Gotcha.  (I took your "I believe so" as agreeing with the OP that the visibility really was 1500m, as the answer to quietflyer's question, rather than agreeing with the implicit doubt of that claim which I guess you must have meant.)

Rain or no rain is not a factor for meeting the legal definition of VFR minimums.
However, at those minima, which is roughly 1 mile/clear of cloud in North America, it is dangerous.
I would fly in those conditions as a bush pilot, say at 500 AGL and a mile vis and a 600 ft ceiling, rain or no rain, but that was over wilderness, on routes that were well known (no towers), on floats where I can put it down on a lake within 5 minutes of flying in any one direction, and I still considered it dangerous and stressful.
Down south in civilization, with radio masts, and now that wind turbine blight everywhere, forget it. If I was forced down below 1000 ft by that kind of weather in the UK or Southern Ontario, I'd be biting my nails.
If you are at 1000 ft and have 3 miles, light rain like that is not too much a problem, as long as you are aware of the issues like visual distortions (objects out front look lower than they are with rain on the windshield) and the nearly saturated air's carb icing tenedency.
Biggest thing is the "spread". Temperature and dewpoint. Bottom line: what is the risk of it closing in on you? Rain tends to reduce the T/D spread to a few degrees.
The temperature trend becomes a big factor. Flying in the morning in those conditions, visibility is likely to improve as the ambient temperature rises. Not too bad.
In the afternoon, watch out, as the 3 deg spread at 2pm drops to a 1 degree spread by 4 or 5, and any more decrease than that, boom, you're in fog. If you see wisps of cloud starting to form at your level, in late afternoon, you are in big trouble.

Well, I know of case where a sailplane pilot was forced to land out on a highway due to sudden snow showers greatly reducing visibility.  I was flying nearby but managed to maintain enough vis to make it back to the airport.  Was a ridge-soaring situation.

Yeah snow showers WAY worse. Late in the season that would be a problem in NE Ontario and conditions that would give 3 mi in rain would give 1 mi in snow.  If you are forced to scud run in settled areas and there is a big highway going your way, get right over that and stay there. At least no towers.

Not directly, however heavy rain will tend to reduce visibility, and obviously you need a certain visibility to remain VMC.


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Are the NPPL minimum annual hours really safe?
I am a Microlight pilot (Ultralight for U.S folks) with an NPPL(m) rating. The minimum requirements for bi-annual license renewal is:

12 hours flying
12 take-offs and landings
1 hour of instruction
Of which 6 hours minimum must be in the 12 months preceding license renewal

Again, to emphasize, this is every 2 years.
Now, in my experience, I feel very rusty after anything more than 2 - 3 weeks off. With these rules, you only need to fly for an average of 30 minutes per month, or 1 hour every 2 months. In theory, when you get your license renewed, you might not have flown at all for 11 months.
My question is - from more experienced pilots (I am under 100 hours), what is the actual safe minimum amount of flying one should do on a monthly basis to maintain, and ideally improve, skill?

Answers will be very subjective as everyone is different.  I don't fly ultralights, but as for small aircraft, I can fly after a couple of years of not having flown and still feel very proficient.  Many factors play into this: knowledge retention / memory, flight SIM, practicing checklist procedures, reviewing manuals, flying with someone else, etc.

I don't fly microlights, but what I do fly is no more complex really. ie, not retractable, not constant speed prop - just your typical single engine piston.
The revalidation requirements for my PPL(A) are the same as you posted for NPPL. And I would 100% agree with you that it does not seem enough. Many years ago at sub 100 hours I used to only really be able to afford/have time for those minimums and I never really felt it was enough to maintain currency.
In the last 10 years, I have maintained a minimum of 50 hours per year and I feel this is just about enough to remain current and confident. If I go more than 2 weeks without flying I feel a little rusty but not critically so. I tend not to go more than 4 weeks ever these days. In the early days of COVID, I went a couple of months without flying, when I did go again, yes I felt rusty, but it was safe enough (I'm still here, the aircraft could be reused!)
Honestly, as well as flying regularly, the other thing that has improved my confidence and skill more than anything else is flying with other pilots. Right hand seat time is almost as valuable as left hand seat. For one thing, you have so much more brain capacity to listen and watch what is going on. Learn new practices, concentrate on navigation.
So in summary:

Fly often, don't leave big gaps.
Find some flying buddies, go places you wouldn't go on your own.

Many thanks Jamie! Not sure if I can get in 50 a year but will see what I can do :)

source: Stack Exchange

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sort: votes


text:
What is the procedure for a fast landing that is too slow for go-around?
Say an aircraft (A320 or similar) on landing, hits the tarmac way too fast and on a short runway, less than V2 but around V1 or slightly over. This could happen if a pilot had recently moved from Boeing and ignored the retard callout for example... or maybe the brakes just stopped working.
The situation would now be too fast to stop short of the end of runway, but too slow for a go-around.
What is the procedure in such a scenario?
Since they're slower and less runway is required to pickup speed in GA aircraft, this question only really pertains to commercial airliners, an A320 or similar. (Also in GA, you can just drift into the grass and use that to slow down, again not really possible in commercial aviation)

First, why should anyone slow below Vref? This would constitute an unstable approach. Second, why would it be too slow for go-around? Unless you have one engine failed at WAT-limited condition, you should always have enough thrust for go-around.

@JZYL Short runway, landed and then forgot to reduce thrust until halfway down it... Also, "shoulds" are not very helpful, as humans inevitably always end up not doing (or doing) things they "should"... this is what emergency procedures are for, a protocol to follow when things don't go as they "should"

Maybe I'm mistaken but the thrust required for -3deg shouldn't be too much for the brakes. Airplanes (the latest generation anyway) are designed to stop with single engine thrust runaway.

This could happen if a pilot had recently moved from Boeing pilots perform months or more of cross-training before being type-certified on a platform that different. At this point it's an incompetent pilot issue, not a procedure issue.

There is no V1 or V2 speed on landing. If you have the speed to fly (down to the landing) you have the speed needed to fly (as a go-aroundj. This question exhibits a misunderstanding of the basic characteristics of flying an approach, landing, and going around, and is neither answerable nor reasonable in its present form.

The system wasn't built to accommodate incompetent pilots.  Everything assumes some minimum standard of human performance.  This is like saying what if I delay getting on the brakes until 50 ft from a traffic light.  Well, you're going through into cross traffic aren't you, and no special emergency procedure is going to help you, unless you're in the Batmobile and can pull the Bat Emergency Brake Handle.
That being said, sometime pilots misjudge things and land long and well, like the late braking at the traffic light, at that point you're going into the weeds whether you like it or not and the emergency procedure is to scream and close your eyes.  It's a dangerous world for everybody but rocks.
Now, to answer your question, there is a procedure called "Balked Landing" which is a go-around initiated after touchdown, or before touchdown but where ground contact is assured.  You put the thrust up, accelerate to Vref, rotate and off you go, if you can.  You have to make an instant judgement call that the balked landing procedure is safer than riding it out to the end of the runway.  Usually riding it out and running off the end is the safer choice because the energy involved is much less when your world falls apart.

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text:
What is a "frozen ATPL"?
I've heard the term "frozen ATPL" and it seems to be some kind of limited EASA ATP certificate. What exactly is a frozen ATPL? What privileges does it give the holder? How is it unfrozen to become - presumably - a regular ATPL?

A frozen ATPL holder is somebody who has passed all the required (14) exams for the issue of an ATPL but does not have the required flying hours. Strictly speaking, there is no such thing as a 'frozen' ATPL, though a number of training schools do use the term:

A Frozen ATPL holder refers to somebody who has passed all the required theoretical exams but does not qualify him to be issued with a full ATPL until he has logged a total of 1500 hours.
A student from a flying school will normally graduate with a CPL (Commercial Pilot Licence) and IR (Instrumental Rating) (CPL+IR). This Licence is known as the Frozen ATPL.

In order to 'unfreeze' the ATPL, the candidate has to complete a flight time of 1500 hours subject to certain conditions:

... ATPL will remain frozen until you have reached 1500 hours of flying time, which is made up of the following criteria:

500 hrs multi-pilot in transport or commuter aircraft
250 hrs PIC (or 100 Pilot in Command and 150 PIC under supervision)*
200 hrs cross country flights (100 as Pilot in Command)
75 hrs instrument time
100 hrs night flight as PIC or co-pilot

A frozen ATPL is the name given to the qualification of a pilot who holds passes in all 14 ATPL theoretical exams. The ATPL becomes unfrozen when the flight experience requirements are met. This experience is normally achieved acting as first officer (flying right seat).

Basically this is the schooling portion of an ATPL, where the experience requirements are met on the job. Having a frozen ATPL is a requirement for employment as a first officer. The ATPL becomes unfrozen on the job when all the flight requirements are met.
Source: aa-fta.com CPL With Frozen ATPL

Since you've quoted a chunk of text from another site, it would be best to add the quoting markup to make clear what's your own commentary and what comes from the other site.

@Pondlife Added it, although it isn't exactly word-for-word.

A 'Frozen' Airline Transport Pilot Licence (ATPL) is the name given to the qualification of a pilot who holds passes in all 14 ATPL theoretical exams. The ATPL would become un-frozen when the flight experience requirements are met.

from: Asian Academy of Aeronautics

I'm not sure what this adds to the other answers, its almost directly the first two lines of my answer, and a direct copy/paste from the link I provided...

This appears to be copied and pasted from another site. Quoting from other sites is fine, but please add a link and use the quoting markup. Otherwise, it looks like you're trying to pass off someone else's content as your own (I'm not saying that was your intention here, only that it might look that way).

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Why are some fuel-injected engines started with the mixture at idle cut-off?
The POH for a C172N with a carbureted Lycoming O-320 says:

STARTING ENGINE

Mixture -- RICH
Carburetor Heat -- COLD
Master Switch -- ON
Prime -- AS REQUIRED
Throttle -- OPEN 1/8 INCH
Propeller Area -- CLEAR
Ignition Switch -- START

The POH for a C172S with a fuel-injected Lycoming IO-360 says:

STARTING ENGINE (With Battery)

Throttle -- OPEN 1/4 INCH.
Mixture -- IDLE CUTOFF.
Propeller Area -- CLEAR.
Master Switch -- ON.
[Beacon and priming steps omitted]
Ignition Switch -- START (release when engine starts).
Mixture -- ADVANCE smoothly to RICH when engine starts.

Why is the fuel-injected engine started at idle cut-off?

Often times fuel injected engines can be difficult to start with the mixture rich, particularly if run recently and still hot.  Following a priming procedure with the electric boost pump then cranking with the mixture at idle cutoff allows the engine to flush out fuel from the injector manifold until an optimal fuel air mixture is reached and the engine starts up.  Quickly moving the mixture to full rich at this point will stabilize the engine at idle with an appropriate throttle setting.

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text:
Why is there a minimum altitude for at least some high-speed jet engine restarts?
While reading this other question about envelope constraints for jet-engine restarts, I noticed something odd in the graph provided (of the relight envelope for the Honeywell HTF7000 medium-bypass turbofan):

(Image obtained from a post by wbeard52, original source unknown but presumed to be either wbeard52 or public-domain)
Notice how, although the airstart envelope extends right down to -1kft pressure altitude at speeds not exceeding 250KIAS, it suddenly jumps up to 5kft at speeds of 250-300KIAS, and then up to 8kft at even greater speeds.  At first blush, I thought that this had to do with the FAA prohibition on exceeding 250KIAS below 10kft, but, on closer examination, it's clear that this can't be the case, since, if that were the culprit, one would expect the lower boundary of the envelope to jump straight up to 10kft at 250KIAS.
The jump in the minimum relight altitude coincides with the minimum speed for a windmill start, indicating that there might be something about the process of windmill-starting an engine that would preclude a low-altitude relight - but, in that case, why doesn't the starter-only-relight envelope extend to higher speeds under the floor of the windmilling envelope?  Is this problem unique to the HTF7000, or do other jets have it too?  What causes it, anyway?

Generally when you see those kinds of limitations it means that the engine or airframe developer had trouble getting successful, repeatable relights outside of the published envelope during development flight testing and you do see it with other engines (the CF-34 that I am familiar with has a similar but much less extreme limitation).
In that case it is probably related to density/velocity of the air flow into the burner can during windmilling and I would imagine that there were issues with getting a successful lightoff every time, or excessive peak ITT during the start, or maybe surging problems or something like that.
You'd have to talk to a Honeywell person for those details.

I realise that the starter-assist envelope goes right up to Vmo at altitude; the part of my question I think you were referring to there was asking why the starter-assist envelope didn't also extend to Vmo even at altitudes below the floor of the windmill envelope.

OK I removed that paragraph.   Well I'd say the same reason applies as with windmill.  Too much flow energy coming in by ram effect.


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Are there any known cases of swing-nose or swing-tail cargo aircraft coming undone in flight?
Large dedicated cargo aircraft frequently (though not always) have swing-nose (Super Guppy) or swing-tail (Dreamlifter, CL-44) designs, in order to allow cargo to be shoved straight in rather than having to pass through a conventional cargo door.
One can imagine the issues that might happen if the nose or tail on one of these aircraft happened to swing open in flight.
Has this ever actually happened?

I was in the Marines at Tustin MCAS(H) in California when the first CH-53E models of large cargo helos were tested and first deployed. I don't remember if it was HMH-465 or -466, but I do remember at least one aircraft suffered an accident where the folding tail mechanism failed. I think it happened on the ground. I am not posting this as an answer because I cannot find a reliable source to confirm this.


text:
Why don’t airliners use stabilizer movement to assist with large pitch control inputs?
Most large airliners not only have elevators for pitch control, but also moveable horizontal stabilizers.  The elevators are used for primary pitch control, with the stabilizers being used to trim the aircraft, and, for some airliners, as an alternate method of emergency pitch control in the event of a loss of elevator control (due to, for instance, a failure of the hydraulic systems powering the elevators, an elevator actuator hardover, or the physical separation of one or both elevators from the aircraft).  Due to their much larger size, the stabilizers have a vastly greater maximum control authority than the elevators (which is why large modern airliners can be trimmed throughout very wide center-of-mass longitudinal-position ranges without having to defair the elevators, and why a stabilizer trim failure is generally somewhat inconvenient); however, despite this, few, if any, large airliners use the stabilizers to assist the elevators when making large longitudinal control inputs (for instance, when taking evasive action to avoid a MAC, or when recovering the aircraft from an upset).
Why is this?  Airliners can and do use secondary flight controls to augment the primaries in other situations; with roll control, for instance, small inputs are handled by the ailerons alone on most aircraft, while the spoilerons1 jump in to help the ailerons with larger changes.  So why aren’t the horizontal stabilizers called on to assist the elevators when large, sudden changes in pitch are necessary?

1: A spoileron is the technical term for a spoiler that is also used for roll control in flight (these are usually the same spoilers as those that can be extended symmetrically in flight to slow the aircraft).  Essentially all large aircraft, and many smaller aircraft, have them to help with large roll inputs; a few aircraft, such as the Mitsubishi MU-2, have only spoilerons, with no conventional ailerons.

Without references, I believe the stabilisers are typically controlled via a jackscrew or similar, and are thus quite slow to move.

who said they don't? (i.e.: citation needed).

Is pitch rate somehow too slow you'd need to augment it?

The L-1011 had an all-flying tailplane. Hasn't been repeated since.

@SomeoneSomewhere And if they were faster they would be very heavy and you would need to make them withstand any tendency for flutter - so even heavier. On top of that: elevators change the camber which is actually quite efficient for deflecting air a bit up or down to counter small disturbances.

There are no regulations requiring airliners to have this kind of high maneuverability. Airliners are designed to be safe and stable. It's more important that pilots are trained to get out of a situation with unnatural pitch than be able to quickly get into such a situation. Voluntarily adding a new system to automatically move the THS to improve handling in situations that are highly unlikely to occur is not without risk. There must be some additional benefit.
In general airliners are more concerned with having too much pitch authority rather than too little, as they spend most of their time in the air at speeds where the elevator has plenty of authority. Fly by wire systems can help this by limiting control inputs to avoid over-stress on the structures. They protect the low end in a similar way by limiting angle of attack.
At low speeds sudden pitch changes would put the aircraft in danger of stalling, as airliners typically don't have the kind of thrust needed to sustain high pitch attitudes, or the type of wings that operate well at high angles of attack. The pitch trim is also not very fast, so it's unlikely that there would be enough thrust to sustain a maneuver that would benefit from moving the entire stabilizer. And at the end of such a maneuver the airplane is left way out of trim, at an extreme pitch attitude, with airspeed either increasing or decreasing dangerously. This might be more dangerous than whatever the pilots were trying to avoid.

The elevators hydraulic actuators are quick response devices, the THS is screw operated and therefore is slower to response.
Therefore it’s normal to use the elevators for short term action and theTHS for long term action.
For safety you can’t rely only on elevators or only on THS. One system should be able to neutralize the other in case of failure.

I don't understand your last sentence. They can't both have more authority than each other. I think that recent experience has shown that the THS overpowers the elevator.

Normally at long run the elevators are aligned with the THS thus reducing the drag, but in case of trim runaway the elevators should be able to immediately neutralize the THS effect. The opposite is also true, I.e. the trim to neutralize the elevators uncommanded movement, but this is less probable.

Remember, airliners are all about passenger comfort.  Secondly, one must check the G load stress limits of applying elevator and stabilizer trim for pitch, especially for negative G's.
As an emergency evasive maneuver, the pilot may prefer to roll the plane to drop it and pull positive Gs.  More so, they would prefer to know what was around them.
Airliners are so massive and fast that any abrupt input would most likely be to little, too late.

An emergency evasive manoeuvre will almost always be done exclusively vertically, because it is simpler, faster and less risky. Turning requires banking the plane first, which takes precious seconds, and it is harder to judge the risk of collision due to the speeds involved. For vertical avoidance, vertical speeds are always rather small and comparing altitudes is reliable.

Agree with you there Jan, but a roll at constant power will immediately cause the plane to descend and turn, add in some elevator and it is "bank and yank". This would be last second desperation.  The gist is a sensible elevator design would be slightly below the G load limit for vertical evasion.  With advance warning (and communication between aircraft), yes, an altitude change would work best.

While roll at constant power will indeed cause the plane to descend, it will only be significant at higher bank angles. You are still at 0.72G vertical at 30°, only get down to 0.5G at 60° and to 0G at 90°, and it's going to take a couple of seconds, because the roll rate will be maybe 20°/s. With elevator push you are at -0.5G in under a second.

That is good info.  I'll add in chop the throttle.  We could work on it in the simulator.

Don't forget that the planes won't avoid each other if both start to descend. One has to climb…


text:
What structural design methods were used for early turbojets?
I have had this question for long time. Can anyone please give me some references on early turbojet engine design methodologies?
For example P&W J57 which was designed in early 1950's: How were vibrations, resonance and aero loads calculated and analyzed, most probably without having computers? I'm not too sure whether there is any closed form analytical solutions anyway.

For vibrations and rotor dynamics, look up the Myklestad-Prohl method. It is amenable to hand calculation and gives a sufficient level of accuracy for basic design calculations. Published in the mid 40s


text:
What are the differences between VORTAC's and NDB's?
What are the differences between VORTAC's and NDB's?

The VORTAC indicator in the cockpit tells you which radial line connects your current location with the ground station you are tuned to in degrees referenced to local magnetic or true north. NDB broadcasts a signal which contains no direction information; the NDB indicator needle in your cockpit only tells you how many degrees left or right you must turn your plane to follow a line leading to the ground station you are tuned to.
If the VOR transmitter on the ground contains a transponder and your receiver is appropriately equipped to send that transponder a signal, the VOR system can also tell you how many miles away from the ground station you are in addition to which radial you are on. this is called DME, for Distance Measuring Equipment. NDB systems cannot do this for you. VORTAC (VOR + TACAN) always have DME equipment.


text:
What happens if you do emergency landing on a US base in middle of the ocean?
A theoretical situation.
I fly from Honolulu International to the Bejing but my private jet gets fuel starvation and then I land on the Wake Island airstrip.
What happens next? Would the military give me fuel or they would give me shelter and tell me to stay? Did such things ever happen?

tangentially related: https://aviation.stackexchange.com/q/32427/13842 (specific to Area 51)

I'd like to see this question reposted except asking if it's a North Korean airbase.

@Dai I will post a related question just for you :D

"give me shelter and tell me to stay" is a nice euphemism for what they might really say.. :)

Not so theoretical:  In 2016 a Delta A320 landed at Ellsworth  AFB by mistake!!  http://avherald.com/h?comment=49adef6e&opt=0

Wake Island has had aircraft divert there before, as it serves as an ETOPS diversion airport.
Per the remarks on AirNav and the NOTAMs:

RSTD: VERY LIMITED OPERATIONS STATUS, AVBL FOR EMERG LDG AND MIN PRIORITY TFC.
TRAN ALERT: SVCG FEES RQD. TRAN SVC HRS 2000-0400Z (0800L-1600L) TUE-SAT. CLSD SUN, MON, HOL.
FUEL: FLIGHT CREW REQUIRED TO ASSIST IN REFUELING. J5(MIL). FLUID - W, SP, PRESAIR.

It's possible you could plan to fly through there with prior permission, as with most military fields. AirNav reports 2% of the average of 49 operations per day are transient general aviation, so it's not entirely military, but government and contractors probably make up most of this.
If your emergency is just that you forgot to have enough fuel, you should be able to get more fuel and depart again, for a fee. If there is a fuel leak or some other maintenance issue, you could be in for a longer stay.

RSTD: NO AIRCRAFT MAINTENANCE AVBL.

As with the airliner that diverted, maintenance equipment and personnel will have to be flown in for any work that needs to be done.
You should be in contact with Oakland ARTCC through San Francisco ARINC in the oceanic airspace, and can call base operations ahead of time to advise of your needs. If it's outside of their normal staffing hours, they need at least 30 minutes notice to open back up.

"2% of the average of 49 operations per day" In other words, one flight per day. I'd say that something that happens, on average, every single day is pretty common.

I wonder whether the "transient general aviation" there includes contractors and other government agencies that are not part of the military, but who are actually supposed to be there (Department of the Interior for the Wildlife Refuge, for example.) Also, an average of 1 flight operation per day would really mean a plane every other day (1 landing, 1 takeoff each.)

It sounds like they have JP-5 fuel (J5?) -- is that equivalent to Jet-A, or would an airline need to ship in fuel if they had to refuel? This answer notes the differences but doesn't say if a civilian plane can fly on JP-5)

@Johnny Whether JP-5 works is irrelevant; if it's not certified to work, which most civilian engines aren't, then it's not legal without a ferry permit, which will probably cost more time and money than somehow shipping in Jet-A.

Landing at a military base is not off limits to civilian aircraft but typically requires some pre-approval. In an emergency situation (and declared over the radio) most military facilities will be helpful. If you came diving in with out any radio announcements and on an apparent crash course the situation may not play out in your favor. But a stable glide in approach with announcements should be safe. You will have lots of questions to answer on the ground though.
I’m sure you will be scolded quite a bit for departing without enough fuel and an FAA/NTSB incident report will need to be filled out.
Fuel may be a bit tricky (although I’m sure you can get some). If it’s a base there may be no way to actually sell you the fuel as the military is not really a retailer. It’s likely that you will have to submit some forms etc etc but it’s unlikely they will keep you stranded.

Many years ago, I had an unexpected landing at a non-towered military base.  I did not need fuel which made things easy.  The base stored nuclear weapons, and we were escorted at all times, until we were able to depart.  Security was annoyed, but polite.  Since we did not leave the ramp, there was no paperwork that we needed, however we did provide the MPs identification, and an explanation as to why we needed to land there.
That was several decades before 2001, so the welcoming committee might have a slightly different posture today.
From a subjective standpoint, people are human, and aircraft are imperfect machines, and there has to be recognition of that. Long established maritime law recognizes that.
Also, the ramp personnel explained that obtaining fuel would have been problematic and potentially required substantial delay.

So why did you have to land? Weather?

The military understands that a distressed aircraft is a priority situation in terms of safety.  When you are an emergency aircraft, all available resources will be provided to you.  Once the emergency is complete, the situation will change depending on where you are and what resources are available.  They will follow some security protocols initially and it will be slow and cumbersome.  Then you’ll have the FAA to deal with.  But you’ll be safe, and as a guy who has been a distressed aircraft and damaged a plane on landing, you’ll be one happy camper to be uninjured and healthy.
Long story short, passing up a safe landing area just because it’s military is crazy.
“Who are you and why did you land here?”
“My name is Jon and I had an inflight emergency that forced me to land here.”


text:
Do aircraft really have text communication over FMC?
I saw a photography that is obviously Photoshopped that sparked my curiosity
Does aircraft have text messages transmission? Can text messages or text strings be transported over the air like transmitting METAR strings over a frequency like ATIS? I remember something about in flight printers that would print hard copies of mid-flight flight plan changes so perhaps something like that can be theoritically used for transmission.
In a simple manner. Is communication over FMC ever done?

Yes. Text messaging over ACARS has been commonplace since the 1980s. It is air-to-ground and ground-to-air, not air-to-air. It is commonly used to exchange flight plans, weight and balance data, ATC clearances, schedule updates for passengers' connecting flights, and other operational purposes, but also sometimes for fun (e.g
birthday wishes, sports game results). It's primarily used between an aircraft and the airline's dispatching department, but can also be used directly between the pilots and ATC under some circumstances.

In my previous company the ground staff could message the crew in flight and vice versa. This was the usual means to communicate Gate assignments or special requests from passengers in flight.. short connections etc. Once in a while you would get requests for football scores..Formula 1 results.


text:
Why would a pilot use ailerons for countering asymmetric thrust in mid-flight?
A inexperienced 747-400 pilot used ailerons for counteracting asymmetric thrust in 1998 aboard United Airlines Flight 863 (YouTube recreation).
Why would an airline pilot do such a mistake? Why would a pilot disregard the counter yaw training he got from the Baron 58 to the 737?
Is he the only pilot that did this or are there other pilots that do the same mistake too?
Perhaps he simply forgot rudder.

This AOPA article "PROFICIENT PILOT LAZY-RUDDER SYNDROME" written about this incident, presents an interesting point of view on the matter, that basically good design and complacency leads to little regular rudder use so in emergencies its initially over looked.

This pilot might have been affected by "lazy-rudder syndrome," the
  reluctance to use a rudder to the extent dictated by given
  circumstances. Some believe that this reflects a general decline in
  basic stick-and-rudder skills. A commonly observed symptom of this is
  lowering the right wing during initial climb after takeoff to
  incorrectly compensate for a single-engine airplane's left-turning
  tendency.

You do that stuff every year in the sim (your first V1 cut during your initial course in a jet is usually quite entertaining), but you never really know how anyone is going to perform until the real deal happens. 98% of the time the training and drill ensures that people can perform, but there are no guarantees, and sometimes people go straight to mental saturation or mental confusion mode even though they passed the simulated emergencies.
Another factor in this case:
In a twin, when an engine fails at takeoff thrust, they yaw pretty hard and start to roll hard immediately (because of the sweep of the wings), and both the yaw and the follow-on roll are really obvious.  If you do nothing with your feet you will find yourself with full aileron and the thing is still rolling over into the dead engine.
With the #3 going south in a 4 engine airliner, the asymmetry is more subtle; the brick (skid indicator) doesn't slide all the way across, and you may not need anything close to full aileron.  So not reacting the the engine failure with rudder doesn't have the same holy crap aspect to it and moderate aileron keeps the wings level, but you are still in a significant side slip in a giant flying barn and it kills the rate of climb.
So a pilot who gets that kind of surprise, new to the type, being mentally led astray by the noises that could be interpreted as tires blowing, it's not too hard to see that kind of reaction as a possibility.
What gets me is the Capt not really doing anything at the critical time.  Very strange. I'll bet the Capt probably got in bigger trouble than the FO in the aftermath.

Not sure if everything that went on was in the video, or if video producer really understood what SHOULD have been done in that situation.  Biggest surprise watching was they didn't immediately reduce pitch when engine went, and allowed airspeed to deteriorate.  That may have been the better subject (along with almost flying into the mountain).

Well if you're hand flying you just fly the flight director and it'll tell you what to do with pitch based on the speed selection (they should have been in speed mode by then).  I think the FO was in brain freeze mode because he didn't comprehend what was happening and was probably fixated on just leveling the wings, ignoring the pitch command and the brick.  The capt should have intervened a lot earlier tho.

Using ailerons to counter asymmetric thrust is a known technique and not necessarily a mistake, especially when flying a plane that is not designed for aggressive ruddering.
Asymmetric thrust creates yaw towards the side of the "dead" engine.  Using a twin engine as a simple example, we want to create a yaw torque away from a left dead to counteract asymmetric thrust. Rudder away (to right) is one method.
Rolling away (to right) will indirectly create right yaw force as follows: dead left engine, roll right, slip right, plane moves laterally right, side force created on RIGHT side of tail, tail is pushed LEFT (nose is yawed right).
The procedure to counter an engine out certainly would be in the POH of the aircraft.
Rather than say one is right or wrong, it may be best to get expert training for that particular type of aircraft.
Theoretically, both methods will work.  Using opposite rudder creates drag too.  The question is which method works better for the 747.  As far as decrying "lack of stick and rudder skills" (from the peanut gallery), no, lack of engine out training, and, perhaps, too many cooks in the kitchen.  Nice video. However, one of them knew to check the airspeed.
It may be possible to use both aileron (spoileron) and rudder together.

Best to compensate asymmetric yaw with opposite yaw directly. Direct control of only the parameter in the 6-DoF matrix that requires correction.

Except if the rudder may tear off.  The real mistakes were loss of airspeed and lack of awareness of the terrain.  The 747 cleared the mountain on 3 engines!!!  Amazing.

In the long run you want to do three things:
One: immediately arrest the initial yaw ( heading change) toward the bad engine.  In the short run you can view the rudder as being the most important control for this purpose, but in the long run other things play important roles (see below).
Two: eliminate all sideslip so a yaw string (if it were present) would be centered.  This is accomplished by putting the rudder in the position that almost centers the ball, but not quite.  Typically it should be left about half a width toward the good engine.  The reason for this is given in a related answer (link to be added.)   This ball position should held while turning as well as while flying in a straight line.
Three: adjust the bank angle  to eliminate any heading change that may have developed after accomplishing step 2 (unless you are trying to turn.)  This may be accomplished with the ailerons. Given the condition established in (two), this will require a slight bank toward the good engine.  After all, the slip-skid ball acts like a bubble level (in reverse- so a pendulum really) whenever heading is exactly constant, so it is clear from the ball position what bank angle must be required to hold the heading constant.  The reason for this is given in the same related link noted above.
Functionally, the same result arises- at least when the goal is to simply fly in a straight line-- if the pilot uses rudder to hold heading and aileron to set the ball position, but this is really kind of a backwards way of doing things.  Just as it is possible to fly blind using a turn rate indicator using the ailerons primarily to control the needle, and the rudder primarily to control the ball, or vice versa.  Most would agree that the former is the better way, but both can accomplish the same result, due to feedback loops.
Anyway, anything that prevents the plane from rolling toward the dead engine is a good thing-- once a turn starts, it tends to continue- so adding an aileron input early in the game doesn't necessarily hurt anything and will probably help a least a little bit, even with no rudder input, as long as the aileron design is a style that doesn't create appreciable "adverse yaw".
I guess this answer doesn't really address why this particular pilot did what he did-- why he omitted any rudder input-- lack of recent training, poor training, poor understanding, too much time spent flying maneuvers that only require yoke inputs and not rudder inputs,  or ???

disclaimer - I don't fly twin or multiengine planes


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How will the lack of ground stations affect navigation?
VOR's and NDB beacons are getting closed day by day and they were used for making and then referencing the holding patterns and the entry procedures and how they were named.
So

How will we make holding patterns and entries from now on? What will be base them from now and how will we name them?
Will the GPS approaches replace other approaches? (Which will make GPS mandatory at least for Class B airspace I Guess)
If GPS approaches doesnt replace them... Will the old names be kept for holding patterns and entries? Will we still say RW29 VOR approach and missed entry procedures?

GPS/WAAS will replace all but ILS in the end. Even now, with graphic displays, smart-lookup from databases, and a line to follow presented to the pilot, VOR use is rapidly falling by the wayside, and point to point navigation will become the norm (and that was occurring in 1996 even, I recall getting cleared direct to a waypoint that was off my paper chart and having to ask for a heading to put in the autopilot to fly the plane while I found it on the chart).  In my airplane, my AVIDYNE IFD-540 does all the work, and I have ILS for precision landings and VOR if needed. Nearby VORs are going away.  DME and ADF were pulled out of my plane years ago.

I'm kind of glad I lived through the VOR years, now that we know they're destined for the history books. Something to look back on with nostalgia, and admire the technology.

GLS/GBAS/LAAS will replace ILS. The issues with ILS are arguably worse than the issues with VOR.


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How feasible digital radio communications would be?
Its been over 100 years since we first flew and we still use analog radio with parasites and "radio effect" which changes your sound.
Why don't we ditch the old system and make a mandate a new law where any aircraft that wishes to fly in a controlled airspace has to be equipped with two digital radio communication systems?
What would the coverage costs be like? Doesn't digital systems require less power and antenna size etc to work which would make it better?

What is the benefit? Just better audio quality? How do you justify the potential billions in implementation costs for that? How do you justify it to the GA community when analog radios cost $2000+, much more for NAV/COM?

Also for commercial operators, do they have to have 4 radios now? You can't mandate other countries, so an international flight would need both...

@RonBeyer I thought it would be a good idea to replace old analogue systems with digital systems that can go out further.

Further would be a problem though since the limited frequencies. I can talk to Minneapolis center from Green Bay, so I don't think that distance is really an issue currently. Local airports don't need the range because they don't need to talk to aircraft they can't control.

Digital systems can have data corruption as well, so I don't see how going from analog to digital in this case solves an actual issue

@RonBeyer what about the costs for airports to operate the radio? How much would an theoriticaly digital telecommunnication system apporximately cost compared to an analogue one?

What's the actual issue?  I think mose of the "parasites" are just local CTAFs all stepping on each other. Digital radio would be no different.  Too many airports too close together, and planes near them transmit and those airborne signals go very far.

The cost to do this would be mind blowing, and out of all proportion to any conceivable benefit. Any equipment certified for aviation is absurdly expensive, and this idea would require every radio in every aircraft + ATC facility to be replaced. Plus, during a transition period, somebody (either every ATC or every aircraft) would have to be dual capable. Plus, you'd need frequency spectrum to run both at once during the transition. And all to gain what? Because digital is cool? Bad plan.

You may be aware that CPDLC is a digital-based communication system between pilots and ATC.

Actually, the standards are in place and the system was been demonstrated about 15 years ago. The FAA program was NexCom and was based on VDL Mode 3 radio system. Using TDMA access and D8PSK coding, it put 4 digital channels in the bandwidth of the current VHF 25 kHz frequency assignments. Each digital channel could be used for CPDLC datalink or a digital voice channel.  In the end, the benefits didn't justify the costs. The benefits of CPDLC in the current system pulls enough users off the voice channels to keep the system within capacity.

@Gerry "4 digital channels in the bandwidth of the current VHF 25 kHz frequency assignments" ...and now at least Europe is well underway in switching to AM with 8.33 kHz channel spacing, which fits three analog channels into those same 25 kHz, and does so without a major equipment redesign, and maintains similar audio fidelity to 25 kHz AM in practice while allowing narrower receiver filters which should in principle reduce the noise level slightly thereby improving the S/N ratio. (Modulating from 12 kHz of baseband audio in aviation would likely be beyond useless.)

Digital is not always better.  Digital modes have been created for amateur radio use; the amateur radio VHF 2m band (144–148 MHz) is very similar to the VHF aircraft band (108–137 MHz).  I have a radio that uses both FM and a digital mode on the amateur 2m band.  Here are some notable differences between FM and digital:

When the signals are strong, the sound quality of FM is slightly better because there are no digital artifacts
When the signals are weak, digital sounds better because there is no static
When the signals are very weak, FM is definitely better because digital either degenerates into unintelligible loud tones ("sounds like R2D2" is what hams say) or is not decoded at all, but analog signals can still be understood with difficulty
Only one digital signal should be transmitted at a time on a channel; if two signals are there at the same time, the stronger signal might get through, but more likely neither signal will get through

The reason that old-fashioned AM has been kept for all these years is that if two signals are there at the same time, both signals can be heard and understood (perhaps with difficulty).  This is a significant benefit; a quieter signal, perhaps from an aircraft further away from the airport, has a much better chance of breaking through to be heard on a busy frequency.  FM and digital modes can't offer that benefit.
Digital radios are not intrinsically more capable than analog radios given the same power levels.  Digital radios can use slightly less bandwidth for the same audio quality, packing more channels into a band, but that's not very relevant for aviation.
The antenna size varies by the frequency, regardless of whether the radio is analog or digital: the higher the frequency, the smaller the antenna.  Switching to digital wouldn't make the antennas any smaller, unless the frequency band changes also.  A higher frequency band would make the antennas smaller, but finding a new large frequency band for aviation use worldwide would be very difficult.

A requirement for a single signal transmitted at any one time is not an inherent property of a digital modulation. TDMA (time division, multiple access) is a well-established method of allowing multiple transmissions to share a single frequency range that really can only be implemented with digital modulation, as it requires transmitting bursts of data in faster than real time, with a waiting period in between bursts. TDMA does however usually require that transmitters cooperate somehow, which could be problematic in an environment where the set of transmitters in range changes continuously.

@aCVn TDMA, CDMA, and other digital multiplexing schemes aren't practical without something like a mobile phone tower coordinating things, which is why digital two-way radio systems (meaning not mobile phones) don't use such schemes.

A MATTER OF COVERAGE:
Digital radio requires higher emitting frequency using pulse modulation or other techniques
analog modulation requires a carrier which could be of low frequency such as in VHF or better in HF
For instance HF radio communications are used in those areas where VHF radio communications are not available due to their limited signal coverage, HF radio signals propagate through ground waves, that are reflected and /or refracted, so the transmission is not linear and will transmit very far.
So analog transmission may have a much larger coverage


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Why does the A-4 Skyhawk sit nose-up when on ground?
The rear of the plane is nearer to the ground, while the front part of the plane is away from the ground (see image below).
Other planes are more flat.
I think it was for high AoA but these planes are carrier operated so I don't think there is much sense for that.

(wikimedia.org)

Not sure what you’re asking.  Are you commenting that it dits nose high in its landing gear?

The landing gears arent the same height which gives the plane a "taildragger posture". Why?

@CarloFelicione Its best observable in the Wikipedia. Open its article and CTRL+F "color scheme".  (Wikipedia is banned I cant give you the link for the image)

I think most of what you are seeing is just perspective. I think the "flat A4" in the upper right corner may be parked on a hill or something. I'm not sure how the F4 is relevant to the A4 question though?

@RonBeyer as an example for an "non tilted" plane

The A-4 had a mechanically-simple but effective high-lift system that relied on gravity and air pressure to automatically deploy. Not sure about the actual mechanism, but I remember reading somewhere that the high pitch angle helped the deployment.

This was pretty common on naval aircraft from that era which used the launch bridle catapult interface. It gave the aircraft a high angle of attack during launch and helped the aircraft get clear of the bridle at the end of the launch stroke. It's noticeable on a wide variety of aircraft, including the F7U-3, F4D, A-5, F9F, F8, Super Etendard, Buccaneer, F3H, just to name a few.
Even the F-4 did. The nose landing gear oleo strut could be extended to give a nose high squat for cat shots:

(theaviationgeekclub.com)

I like this answer better than mine.  As a side note you could note that the A-4 gear was designed to be tall overall to give sufficient ground clearance to carry a nuclear weapon.  Sources: For corroboration, "The long landing-gear struts were dictated by clearance requirements for large stores carried beneath the wings on either side and between the main landing-gear legs." https://history.nasa.gov/SP-468/ch12-7.htm (thanks ymb1), http://www.f16.net/forum/viewtopic.php?f=46&t=27254 .

The latter suggests that there were issues with the nose dipping too low during catapult launches and less-than-optimal landings but it's still not clear whether the tall nose gear was actually intended to help prevent that in any way.

Article of peripheral interest on "bridle catchers" and launch bridles: https://www.thedrive.com/the-war-zone/7099/__trashed-9 .  Also https://www.patriotspoint.org/news-and-events/navy-catapult-launch-improvement-1962/ .  Google "launch bridle" for more.

Also http://thanlont.blogspot.com/2011/01/catapult-innovations.html

This should be the accepted answer.

Then why doesn't F4 have that too? After all its designed to be an carrier aircraft with folding Wings right?

Ah but the F4 did.  The nose landing gear oleo strut could be extended to give a nose high squat for cat shots https://theaviationgeekclub.com/vintage-video-shows-phinal-f-4-phantom-launch-from-a-u-s-navy-aircraft-carrier/

"The nose landing gear oleo strut could be extended" ... Fleet Air Arm F-4K even moreso, apparently.


text:
Why does this VOR's compass has an arrow pointing north east?
The VOR compass here has an arrow that points to the north east. I never saw an VOR compass like that. What is the explanation?

Everything points to Ozzy Osbourne...

Every VOR compass has a declination one direction or another.  If you've never seen that before, its only because you never looked.

From ICAO SARPS Annex 4:

This is due to the magnetic declination, which varies from place to place, as well as over time.
Note that VOR stations are typically not realigned over time, so discrepancies may arise with respect to the ever changing magnetic north, but in radio navigation a radial is just that – drawn over a chart, and tuned to, it will always be the same.
Further reading:

http://www.magnetic-declination.com/what-is-magnetic-declination.php

So the arrow points to magnetic north?

This answer could be improved by clarifying that the "arrow" in the figure in the original question points to some version of "north", more specifically to some version of magnetic north, which due to various reasons might not be exactly the same as the actual magnetic north but it's pretty close.  I don't think the originally asker had any idea that the arrow was a north-pointing index of any kind at all.


text:
Can ADS-B used for voice communications?
Everyone knows the radio communications doesnt sound great altough they work perfectly.
But can the brand new ADS-B communications be used for carrying audio signal? Would it be clearer?
The ADS-B will be mandatory by 2020 (At least for anyone that wants to fly at the controlled airspaces) so why dont we ditch the old radio system full of parasties and use ADS-B instead for voice communications instead?

Why dont we ditch the old radio system full of parasties and use ADS-B instead for voice communications instead?

Well, why don't we use televisions for washing dishes? Because televisions don't wash dishes.
Likewise, ADS-B doesn't carry an audio signal, so it can't be used for voice communications.
Perhaps ADS-B could be modified to carry voice signals, but this is probably not a good idea. The reason for this is that, while aviation voice communications currently use a band which is 19 MHz wide, the band that ADS-B uses is only about 1 MHz. (The Signal Identification Guide says, "There are two types of ADS-B: one [...] with about 50 kHz of bandwidth;
[and] one that transmits at 978 MHz [...] using a larger bandwidth of about 1.3 MHz".)
Transmitting voice signals digitally is a good idea, but I don't know of any reason why this would be done using ADS-B. It would make more sense to simply design a new protocol from scratch.

It appears that you are mixing up service bandwidth and channel bandwidth.  VHF airband channel bandwidth for voice is usually 6, 8 or 25 kHz. 19 MHz is the combined bandwidth for 760 channels. ADS-B has a channel bandwidth of either 50 kHz or 1.3 MHz. The latter would be sufficient to transmit high quality surround sound.

@bogl Maybe I am. We have a total of 19 MHz of the radio spectrum allocated to aviation voice communications, and I interpreted the linked wiki page as meaning that there's a total of about 1.3 MHz allocated to the 978 MHz band of ADS-B. Maybe I interpreted that wrong, though. I'm also not entirely sure what point I was trying to make with the bandwidths in the first place, come to think of it.

ADS-B is very low bandwidth and is completely unsuitable for carrying voice traffic. The answer to the "why don't we" question is quite simply "it doesn't work that way".

Please see my comment on Terran's answer.

As an additional point... the reason ADS was given its own frequencies was so that other communications would not interfere with the needed Position and Identification information sent out via that method. ADS can in many places surplant the need (though I'm not at all suggesting that it should do so) for primary radar. There are too many things that can end up in the air that primary radar can see which don't have a any transmitters...flocks of birds come to mind, planes with malfunctioning radios, weather balloons or even idiots in lawn chairs with balloons.
By nature -- in radio -- a single station is either listening or transmitting if you have ATC transmitting on that frequency, 3 things will happen.

ATC wont hear all of the other stations transmitting on the frequency,
Any other Receiver wont hear anything except ATC's extremely powerful transmitter attached to good antenna.
Since ATC is stationary on the ground its position, altitude, and all of the other things reported in a ADS packet will be particularly useless to all of the other planes that can also receive ADS traffic.

The last factor is Time all of those ADS identifiers are really really short in time -- way under a second. This is why so many planes can use the same frequency.
Even if two stations step on each other, transmissions have a random delay between them from a given station. Good signal processing can even separate stations that transmit at the same time in some conditions, for instance if each transmitter is slightly off the center frequency differently.

There are a number of reasons using ADS-B's frequency as a carrier for voice communications isn't a great idea. There are a few issues and factors which I believe you're not taking into consideration which, once understood should illustrate why that is not a workable or desirable solution.
First, I'm not going to address this in terms of the UAT system, the fact that it's only used in the US would proclude it's use anyway.
Now, the frequency that ADS-B operates on for transmitting digital data packets is 1090 Mhz. When ADS-B was first designed, in order to minimize the complexities inherent to any work integrating a newer, more modern data transceiver system into an older existing system, eliminating any need for additional frequencies which are only compatible with the new gear, and this would require additional system components to translate or retransmit, is always a smart move.
In the case of ADS-B, the system engineers decided to use an existing frequency by simply building the entire ADS-B system essentially over the existing Mode-S transponder Secondary Surveillance Radar (SSR) systems. In fact, for a short time way back when, an ADS-B signal was actually referred to as Mode-S ES signal, or Mode Select - Extended Squitter signal. The Squitter being the colloquial term for a Mode-S data packet. Therefore, if one wants to fit more data to send, just extend that squitter. Tada!!!
While the Mode-S system does reduce the frequency congestion when compared to the previous generations of transponders (Mode-A/3/C), one of it's primary design goals, even without all the ADS-B noise being added to the frequency, trying to for a voice carrier onto the same frequency would certainly be less than ideal.
Additionally, adding voice coms, even in digital format, would inevitably begin to cause interference with the SSR and transponders exchanging data, so there's that.
When you consider that we haven't even broached the fact that all the air carriers, who are required to be equipped with and operating with a Traffic Collision Avoidance System (TCAS). Wanna take a shot and guess which system TCAS is built on top of? That's right, Mode-S.
I've never heard what it sounds like, but I've got to imagine that when 2 TCAS boxes start chatting feverishly about who goes high and who goes low so they don't collide, it's not a pleasant sound. And these are REALLY important communications which should not be interfered with, cause if you've got 2 TCAS talking to each other, best to let them finish the conversation!!


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What does the future of the weather radars look like?
Planes had weather radars for a long time (Dassault Falcon and Learjet35A) which was useful since you either had to ask ATC, listen the ATIS frequency or ask the flight advisory before flight planning in order to learn the weather.
But we are living at a time of two way transponder communications and more and more of the world (At least the USA) are employing more weather stations and satellites are continously monitoring the world which makes the weather information more and more accessible and in flight Wi-Fi finally arrived!
So. are there plans about sending weather information through two way transponders in the future? Will this hamper the importance of weather radars?

NTSB put out a safety alert after the delay in in-flight broadcast weather was implicated as a factor in 2 fatal accidents. It is not a replacement for weather radar!

In the USA, planes with ADS-B can receive FAA transmitted weather from ground stations for display in the cockpit. It can lag by several minutes.
https://www.faa.gov/nextgen/programs/adsb/pilot/
Planes with XM weather can receive more timely weather from satellite feed for display in the cockpit.
Airborne radar has the advantage of being the most immediate, but you may not be able to see much past what is immediately in front of you, so combining that with ground/satellite feed to give you a view of what is farther ahead would be the best of both.
I have ADS-B in my plane, but I don't do any extreme weather flying, just climbing thru cloud layers to get to nicer weather on top, or dropping thru a layer to land. I'm not out there trying to dodge thunderstorms and heavy rainstorms. If the weather is that bad, I can wait it out.

Since both ground based and airborne weather radar is all about bouncing radio waves off water, the issue is, do you want to send the radio waves from your airplane or from a ground antenna somewhere in the region.  Well, there are advantages and disadvantages to both; one presents a weather "big picture", the other tells you what is going on right in front.
If you have choose, you want an airborne system because that's what is best able to keep you out of trouble right now.  Pilots flying IFR without weather radar could rely on ATC's weather radar for guidance in staying away from severe weather, but this was never considered optimal and airborne radar has always been preferred.
The Storm Scope thunderstorm detection system, that locates and maps lightning strikes, came out in the 70s as a way for light aircraft that couldn't install airborne radar to dodge cells with higher confidence than just advice from ATC. It has its own deficiencies because the really bad stuff is usually associated with water more than electrical charges so Storm Scope couldn't always be depended on the keep you out of the worst of a storm, although it was better than nothing.
I'd say that what you WILL see though (or are seeing already) is a seamless integration of airborne and ground weather radar via various data channels, as well as electrical storm activity, into aircraft displays, to provide the accurate possible presentation.

What I also foresee is the integration of information coming from:

Airborne weather radar
Ground based terminal radars
Satellite radars
Other sources like LiDAR or thermal sensors.

Each of them has advantages and disadvantages. For example, one of the most dangerous disadvantages of airborne radars is the "attenuation", which hides the weather behind a strong signal. There has been accidents in the past directly related to this limitation.
The radar technology itself has a huge limitation to detect certain types of dangerous weather conditions, for example ice crystals, even in high concentrations.
In order to overcome such limitations, the future weather systems most probably will relay and integrate radar along with other technologies like LiDAR (Laser Imaging Detection and Ranging). There is a lot of research nowadays using LiDAR to study weather, it wouldn't be a surprise to see that in the aviation industry in the near future.

I didn't knew LIDAR was being developed. thanks for bringing information and good luck in the site!.

It is quite an interesting technology that also can help to predict turbulence: link


text:
Why buy an new plane or an helicopter?
This really keeps coming to my head.
A brand new 172SP costs a quarter million while a older one (10 years older or a little bit older) costs for less than 100.000 Dollars and the only visible difference is the G1000 NXI and a AoA indexer next to the compass.
Its maybe my ignorancy on the specifications but with the price difference I could:

Buy a brand new avionics suite turning the plane to a spaceship. everything from a autopilot to the Class S transponder.
AUX tanks
And maybe a brand new, upper model engine by selling the original one!

And I would STILL have surplus money!
Things is... As long as the owner of the second hand plane treats the engine good and doesnt abuse the airframe for aerobatics I dont see a SINGLE reason to NOT buy that plane.
So why waste so much money for a factory installed AOA Indexer that can be bought for less?
I am not acquinted with helicopters but the same "250K Brand New vs 100K Owned" thing applies to them too, I see. (Robinson R22)

In my experience, that question generalises quite well to anything. Only reason I see to by new occasionally is if I can’t get what I need second hand or if I absolutely require manufacturer‘s warranty.

@CptReynolds what can't you get second hand and why would you requirer warranty? I am not aware of commerrcial aviation requiring warranties.

Yes, I said you can generalise the question to anything, outside aviation as well. Why buy anything new? Manufacturers warranty: If you buy the brand new aircraft, I expect that if the engine blows after five minutes of flight, you get some money back. If you buy used from a neighbour‘s shady uncle, not so much.

FYI, the G1000 is only available from the factory; you can put other glass in used planes, but not that specific system.

"A brand new 172SP costs a quarter million" I think the new SP's go for closer to $400,000 new.

According to this answer https://aviation.stackexchange.com/questions/11967/what-limits-the-lifespan-of-helicopters  an R22 has to be rebuild at 2200 hours

A 172 was about 20 grand in 1970.  You could buy a pretty nice house for that.  Same today.   New airplanes have ALWAYS been crazy expensive.

@StephenS I think you can buy an G1000 and send the plane to the Textron for the conversion according to the Garmin.com

@StephenS What is so specail about NXI edition anyway...

Why do people buy new cars?  Mine vary between 17 and 31 years old (and the Cherokee is almost old enough to collect Social Security :-)).

@JonathanIrons The G1000 is tied directly into the specific model of engine and vice versa, so that really only applies to an older C172S with a six-pack.  See my answer below on why nobody would do that with previous models.

Because some people like new things... Thats how salesmen stay in business.
There are however some practical aspects to this question and on the tail end of my instrument rating I've been getting serious about buying something, here is what I have found. For the purposes of this answer I'm only going to talk about aircraft that are still in production like the 172 and have been for some time. The only other comparable aircraft is the Piper Archer. Mooney no longer makes the lower power stuff, the early low power PA-28 variants have been out of production for some time and are thus out of scope. In the end it depend s on what you, the pilot/owner/operator really wants out of the aircraft.

While a 1956 172 will share a lot in common with ones rolling off the line now a G1000 cockpit is not a steam gauge cockpit. A G1000 unit, or any of the various glass options for retrofit are NOT cheap to buy and install. Thus if you get a decent, low time 172SP and replace the panel to make it just like a new one, you have already spend about what a new one costs and there may very well be 2000 hours on the airframe already.
The older the plane (generally), the more engines its been through. A well flown early era 172 may very well be on its 2nd, 3rd or 4th engine. These engines could have been overhauled, rebuilt, swapped by various different entities in various ways. There may or may not be a warranty on them anymore and you may have little protection against it blowing out on you. Meanwhile a new plane may come with a warranty which represents real tangible value especially considering the first hundred hours or so of an engines life are quite critical. You can find all of Textron/Cessna warranty info here.
You are buying effectively a 0 time engine (or as low as practical) again you can buy a nice 172 then go spend another 20K, 30K, 40K... putting a fresh engine in it to get a "new" airplane.
The paint and interior are new and clean. There is nothing quite like the tired velour interiors of rental aircraft but even second hand planes often have tired 80's fabric that have seen a lot in their time. A fresh paint job and new interior is not cheap, especially when you realize you need fireproof fabric, may need to take a lot of the plane apart to paint it and dealing with the downtime. We come back to the 80's 172 that needs paint and a costly interior example...
Finally, old planes are just tired. Even planes that look to be in good shape, pass inspections, and fly great dont last forever. Some times you are just taxing along and your gear gives out...

Buying an old plane and making it a new plane may just cost as much as a new plane.

If you put in a new (and probably bigger) engine, new avionics, new interior, new paint, etc., then you almost have a new plane, but once you consider the cost of labor for all that work, you're approaching the cost of a new plane too.  The airframe will still have a ton of hours on it, though, and those may have been very hard hours in the case of trainers like the C172.  That's where most of the remaining difference in price can be found.
So who is willing to pay for a brand-new airframe?  Mostly career-oriented flight schools.  They want to be seen by students (or whoever is paying the bill) as having brand-new, top-of-the-line fleets to justify their high prices, and those new airframes come with glass, which is also valuable for them in particular because that's what their students will likely be using now when they go commercial/airline after graduation.  You generally won't find glass or new planes at flight schools (or clubs) oriented toward weekend warriors, who are typically more focused on the cost than what exactly they're flying.


text:
Who can carry out airworthiness inspections?
My understanding is that aircraft regularly have inspections for defects just like cars in the U.K. have an annual MOT test to check their condition and safety.
My question is, who can do these inspections and what qualifications/certifications do they need?
I'm primarily interested in CAA requirements but FAA requirements would also be interesting to know.

I can speak to the FAA requirements.  The basic requirement for the annual inspection (commercial aircraft have additional requirements) comes from 14 CFR Part 91.409

§91.409   Inspections.
(a) Except as provided in paragraph (c) of this section, no person may
  operate an aircraft unless, within the preceding 12 calendar months,
  it has had—
(1) An annual inspection in accordance with part 43 of this chapter
  and has been approved for return to service by a person authorized by
  §43.7 of this chapter; or...

And the related requirement regarding who can perform this is covered in Part 43 and is in two parts; who can perform the work and who can approve the return to service.
The work must be performed by someone specified in 14 CFR Part 43.3 in which the general case is:

§43.3   Persons authorized to perform maintenance, preventive
  maintenance, rebuilding, and alterations.
(a) Except as provided in this section and §43.17, no person may
  maintain, rebuild, alter, or perform preventive maintenance on an
  aircraft, airframe, aircraft engine, propeller, appliance, or
  component part to which this part applies. Those items, the
  performance of which is a major alteration, a major repair, or
  preventive maintenance, are listed in appendix A.
(b) The holder of a mechanic certificate may perform maintenance,
  preventive maintenance, and alterations as provided in Part 65 of this
  chapter.
(c) The holder of a repairman certificate may perform maintenance,
  preventive maintenance, and alterations as provided in part 65 of this
  chapter.

And the approval for return to service must be per 14 CFR Part 43.7

§43.7   Persons authorized to approve aircraft, airframes, aircraft
  engines, propellers, appliances, or component parts for return to
  service after maintenance, preventive maintenance, rebuilding, or
  alteration.
(a) Except as provided in this section and §43.17, no person, other
  than the Administrator, may approve an aircraft, airframe, aircraft
  engine, propeller, appliance, or component part for return to service
  after it has undergone maintenance, preventive maintenance,
  rebuilding, or alteration.
(b) The holder of a mechanic certificate or an inspection
  authorization may approve an aircraft, airframe, aircraft engine,
  propeller, appliance, or component part for return to service as
  provided in Part 65 of this chapter.

Requirements for mechanics and inspection authorizations are spelled out in 14 CFR Part 65, Subpart D.
The regulations also allow manufacturers and repair stations among a limited number of others to perform the work as well.  (see links)

"The holder of a mechanic certificate" seems vague. What certificate is that? Is there an FAA mechanic scheme?

@Notts90 It means a licensed A&P (Airframe and Powerplant). Mechanics who work on aircraft must go through a lengthly certification process, but that doesn't mean that the person performing your inspection is a licensed A&P, they just have to be working under the supervision of a licensed A&P. It takes 2000 hours of experience to get the A&P license from the FAA.

@RonBeyer so any competent person under the supervision of a licensed A&P mechanic can perform the inspection? Is there a specific name for the license?

In the FAA world, this is a Mechanics Certificate but are more commonly called A&P's. Yes, any "competent" person can perform the work, however it has to be signed off by a certificated A&P in the log book so it would behoove the A&P signing off to verify the work, ultimately their certificate is the one on the line.

@RonBeyer that's the answer I was looking for. Thank you! If you post it I'll accept.

@RonBeyer looking at another page from the link you posted I found this FAQ on mechanics and who can do the role etc. answers my questions for the FAA side entirely.


text:
How are registration numbers assigned?
I'm surprised this hasn't been asked before but I could find any question on here for it.
Who picks the tail number for a new aircraft?
Is it automatically assigned by the authorities you are registering with or can the new owner pick any number as long as it's not already I use?
If it's auto generated by the authorities, can you purchase the equivalent of a custom car registration plate if you want a specific number?
I've tagged CAA but would be interested to know if the FAA is the same.

For the FAA, you can pick a specific N number as long as it isn't registered or already reserved.

@Ron Beyer is correct.  There have been interesting law suits over N-numbers... an early one was N1KE

In the US, aircraft numbers are requested or reserved from an available list by the aircraft owner: N-Number Availability Query.  Then the owner, the manufacturer in the case of new aircraft, submits an application for registration with the reserved or available number.
This order of events (to reserve then request assignment) is important as registration numbers are applied to the aircraft, recorded in logbooks, programmed in computers, etc. before the aircraft certification is complete.
In the US, aircraft manufacturers reserve blocks of registration "numbers" long in advance of manufacture.  A registration request is made to the FAA on the appropriate form at which time a registration examiner at the FAA determines the legitimacy of the request: whether the number is assigned or available to be assigned to the aircraft as requested.
The Canadian process is the same.  Available Marks

It isn't always the manufacturer that submits an application for registration for new aircraft. If you buy your new GA aircraft through a dealer, the dealer will submit the registration information.

It's the owner that signs the original application for a number to be assigned.  Any owner can make an application with another number.  That owner may be a dealer, an individual, the builder, manufacturer, etc.

Having bought and accepted delivery for quite a few new aircraft, it's all driven by what paint is on the plane, and is the N number available. More than one factory has assured me that if I give them a number by 5PM, it will be on the plane the next morning.  It is noteworthy that N-numbers can be juggled between planes.  Only the serial number is sacred, and even then I wonder sometimes.


text:
How are landing aircraft handled during an emergency runway closure?
A Hypothetical scenario

A landing aircraft at a busy airport such as London Gatwick LGW
  has an issue during landing that requires the immediate closure of the
  runway.

My understanding is that there could be several aircraft lined up on approach to land at busy times and more circling waiting to land.
If such an incident as the one described above were to happen how would ATC handle the other aircraft?
Obviously they will almost certainly need to be diverted, would they contact each aircraft individually to give instructions starting with the closet to landing and work back or is there a quicker way to give mass instructions to divert all aircraft?

How BA038 was handled at Heathrow is to me, a model of professionals putting a pre-prepared plan into action in all respects, airborne and ground based.

@Simon great video, kudos to that controller too.

In the case of Gatwick, they switch the arrivals to the emergency runway just to the north that's too close to the main runway to be used unless the latter is closed.

As a tower controller, in case of an unexpected unusual situation for an aircraft on final approach, this will be my list of priorities:

Clear the runway of other traffic
Determine if fire and rescue services need to get involved
(Call fire and rescue services)
Call approach and ask them to stop inbound traffic. In case of other traffic on final behind the emergency, coordinate missed approaches
Instruct other aircraft on final to go around, in accordance with the coordination with approach

The above points will take me no more than 30 seconds to get through. This takes care of the most immediate priorities. I will then await the landing of the emergency plane, and coordinate with fire and rescue as appropriate.
As for departing traffic on the ground - aircraft on their gate will be instructed to stay there. Aircraft taxiing to the runway will either continue to the runway holding point or be turned around to a gate, if available - this depends on whether I expect the runway to be closed for a long time (say, more than 20 minutes). The same, more or less, applies to VFR traffic in the control zone intending to land. They can hold in the air if I expect to reopen the runway shortly, otherwise they might have to find an alternate; I will coordinate any diversions with approach.
Once I have a hold of my own traffic, I will call the operational supervisor and inform them of the situation. They will take care of stopping additional inbound traffic if required, and coordinating with adjacent units and sectors. I might also call approach again directly to let them know how the situation is developing.
It will be up to approach, in cooperation with the supervisor and based on the information I provide, to determine if aircraft on initial approach should be diverted, or if they can hold in the air awaiting a runway reopening. Each individual aircraft will require individual handling, to determine if, where and how they want to divert.
Once the runway is reopened (after fire and rescue have finished their work, the emergency airplane has been removed, runway inspection carried out and so on), I will coordinate with approach and the supervisor to start inbound traffic again (possibly with a reduced rate), and start getting my own departures rolling again.
As you can see, there are a lot of "if's" in the above. A lot of decisions have to be made, and the basis for making said decisions changes depending on the situation. There is no set checklist or rulebook for when something like this happens, because the required actions will vary. But that is what we get paid for after all - as an air traffic controller you have to be creative and flexible, especially when unusual situations occur.

Hmm. Side question that comes to mind reading this, how often does another aircraft in the air become an emergency due to low fuel because whatever it was inteding to do gets shut down. Not sure if seperate question; thinking out loud, should go have a search for low fuel inna bit.

@StarWeaver The flight crew must legally decide to divert before a fuel emergency is inevitable. So in theory, that should never happen.

Your mention of VFR traffic makes me wonder - would you issue a blanket "All VFR flight following services terminated" radio call or would you (have to) specifically address each aircraft?

@FreeMan I would talk to every aircraft. If they are inbound to land, they are already provided with air traffic control service (ATC), not just "flight following" (or the international equivalent - flight information service). I can't just terminate ATC service for controlled VFR flights (and would have no reason to or interest in doing so).

Ah, yes, that makes sense. FF/FIS wouldn't be impacted by a runway closure unless they were inbound to land.

@StarWeaver, extremely unlikely, but it happened in 2014 in India. Two aircraft were diverting to Jaipur, but weather deteriorated there below minima too and the first attempted autoland on the CAT I ILS and had a collision (fortunately not fatal) that disabled it on the runway. The second aircraft fortunately had just barely enough fuel to get back to Delhi and do an autoland also below minima on the somewhat better CAT II there.

The immediate priority is to ensure aircraft separation is maintained, and send out rescue vehicles to the problematic aircraft if needed. Therefore, ATC will:

Issue a "go around" instruction to the next arrival aircraft.
Ask the pilots of the problematic aircraft if they need any assistance.

If rescue vehicles are dispatched, all ground traffic will be stopped. The controller may issue an "all stop" instruction to all aircraft and ground vehicles on the frequency.
Next, the controller needs to assess the situation. How long will it likely take? Is it a steering problem, or is the aircraft burning? If a prolonged delay is expected, ATC will:

Contact the "approach" controller to stop sending aircraft to this airport/to the affected runway.
If the airport has general aviation traffic, ATC may instruct the pilots to keep going around the pattern.
Keep aircraft out of the airport airspace to reduce the controllers' workload.
Notify the "ground" controller/dispatchers to delay pushing back aircraft.
Give taxi instructions to aircraft prepared for takeoff so they can return to the gate.

Actually, tower will coordinate with approach immediately, not only after evaluting the situation. The missed approaches must be coordinate, and a runway closure of any length must be coordinated - doesn't matter if it's 1 minute or 1 hour.

Depending on how long the runway is expected to be closed (from a few minutes to clear it of FOD to more than a few hours because the aircraft wreckage is still on the runway) the tower will either put the incoming aircraft in holding patterns until the issue is resolved or be diverted to other runways which may require going around and lining up again.
Each aircraft will get its own instructions. There are at least 2-4 minutes between landing aircraft for separation/turbulence reasons so there is plenty of time to handle them one by one.

Where does "5 minutes between landing aircraft" come from?

@WayneConrad misremembered data, actual numbers in http://aviation.stackexchange.com/a/26184/609 are a bit shorter

@ratchetfreak Those only apply in case of wake turbulence concerns. A medium following a medium or a heavy following a heavy can be less. A quick search suggested 60 seconds separation for departures on a given runway and 3 nm for arrivals (60-90 seconds, depending on approach speed.) It seems like I heard a while back that ATL might be down to 45 seconds between departures now, but I might be remembering that wrong.

@reirab 45 seconds between departures sounds plausible when applying reduced runway separation standards

@reirab: Or, presumably, a heavy following a medium.


text:
Is there a definition of light/medium/heavy aircraft?
I'm surprised this hasn't been asked before but I couldn't find it by searching.
For separating arriving aircraft, ICAO PANS-ATM-Doc 4444 Air Traffic Management refers to aircraft as "LIGHT", "MEDIUM" or "HEAVY" but I cannot find any definition of what makes an aircraft fall into any particulate category.
I would of expected a limit on MTOW for each category, does such a definition exist or is it more of an informal definition?

5.8.2 · Arriving aircraft
5.8.2.1 Except as provided for in 5.8.l.l a) and b), the following separation minima shall be applied.
5.8.2.l.l The following minima shall be applied to aircraft landing behind a HEAVY or a MEDIUM aircraft:
a) MEDIUM aircraft behind HEAVY aircraft- 2 minutes;
b) LIGHT aircraft behind a HEAVY or MEDIUM aircraft- 3 minutes.

Section 4.9.1.1 of ICAO PANS-ATM-Doc 4444 Air Traffic Management defines LIGHT, MEDIUM & HEAVY aircraft for the purpose of wake separation:

4.9.1 Wake turbulence categories of aircraft
4.9.1.1 Wake turbulence separation minima shall be based on a grouping of aircraft types into three categories according to the maximum certified take-off mass as follows:
a) HEAVY (H) — all aircraft types of 136,000kg or more;
b) MEDIUM (M) — all aircraft types less than 136,000kg but more than 7,000kg; and
c) LIGHT (L) — aircraft types of 7,000kg or less.
4.9.1.2 Helicopters should be kept well clear of light aircraft when hovering or while air taxiing.
Note 1.— Helicopters produce vortices when in flight and there is some evidence that, per kilogram of gross mass, their vortices are more intense than those of fixed-wing aircraft.
Note 2.— The provisions governing wake turbulence minima are set forth in Chapter 5, Section 5.8, and Chapter 8, Section 8.7.3.

Let me add the proposed Super category. According to Wiki and this article:

ICAO mandates separation minima based upon wake turbulence categories (WTC) that are, in turn, based upon the Maximum Take Off Mass (MTOW|MTOM) of the aircraft.
These minima are typically categorised as follows:

Light (L)– MTOW of 7,000 kilograms (15,000 lb) or less;
Medium (M)– MTOW of greater than 7,000 kilograms,
   but less than 136,000 kilograms (300,000 lb);
Heavy (H)– MTOW of 136,000 kilograms (300,000 lb) or greater.

A fourth category is currently being taken into
    consideration by ICAO:¹

Super (J)– Refers only to the Airbus A380

Even though the resolution to add the "Super" category is still under consideration, both the FAA (see below) and EUROCONTROL have already implemented guidelines concerning the Airbus A380.

(emphasis mine)

Doesn't "super" also include the An-225?

@StephenS Apparenty FAA says yes but ICAO says no. Maybe it doesn't matter that much because the An-225 is such an exceptional and rare aircraft compared to the A380.

Doesn't matter at all anymore, unfortunately, @PerlDuck.

Oh yes, @randomhead, oh yes

The FAA answers this question here: Weight Class

Weight Class
  Weight class is based are assigned by APO130 based on the TFMS observed aircraft codes. There are 6 categories -- (A) Heavy, (B) B757, (C) Large Jet, (D) Large Commuter, (E) Medium, (F) Small.
(A) Heavy: Any aircraft weighing more than 255,000 lb such as the Boeing 747 or the Airbus A340;
(B) B757: Boeing 757 all series;
(C) Large Jet: Large jet aircraft weighing more than 41,000 and up to 255,000 lbs such as the Boeing 737 or the Airbus A320;
(D) Large Commuter: Large non-jet aircraft (such as the Aerospatiale/Alenia ATR-42 and the Saab SF 340), and small regional jets (such as the Bombardier Canadair Regional Jet), weighing more than 41,000 and up to 255,000 lbs;
(E) Medium: Small commuter aircraft including business jets weighing more than 12,500 up to 41,000 lbs such as the Embraer 120 or the Learjet 35; and
(F) Small: Small, single, or twin engine aircraft weighing 12,500 lbs or less such as the Beech 90 or the Cessna Caravan.
Unknown; refers to unspecified equipment.

"Light" Aircraft follows the same definition as "Small" in the above text.
Wake turbulence is no joke - you can feel it if you come in behind a larger aircraft even several minutes after it lands, and often even if you stay above its glide path and land beyond its touchdown point, as you should.
There was a Grumman Tiger landing at my local airport that didn't pay attention, ignored the tower's "caution wake turbulence" warning, and got flipped inverted and subsequently crashed as a result of wake turbulence from a UH-60 military helicopter that had departed several minutes prior. The pilot, very fortunately, walked away but the aircraft was ruined.
Note that even though helicopters are not mentioned in your post - any helicopter leaves persistent rotor wash and you should be extremely cautious and wait several minutes before attempting to takeoff or land anywhere a helicopter has been.

This question is about ICAO L/M/H categories, not about FAA classifications

@60levelchange Pugz was describing the Wake Recat categories; the FAA also defines "heavy/large/small" in a similar way to ICAO's "heavy/medium/light," although the dividing lines are placed at different weights than ICAO's lines.

please note that there is a "Super" category only for A380 as the wake turbulence can cause issues even for Heavy aircraft if they use the same seperations as "Heavy-Heavy"

Welcome to Aviation.SE! If you use the answer field, it is expected here that you provide a full answer to the question. This currently reads more like a comment to the other answers. Could you expand this a bit to turn it into a complete answer?


text:
What procedures are followed for a planned landing in a field?
If an aircraft was making a planned landing in a field/sports ground/other large flat area what landing procedures would be followed?
My thoughts are that it would be very similar to a non-towered airport, with self announcing and flying a bit of a pattern to check the landing area is clear.
Obviously this is more likely to apply to helicopter but it could potentially be a plane.

That field might actually be an airport... https://youtu.be/X1qLn_wf4uI?t=6m30s

@MichaelHampton nice video but I'm interested in the case where it's not an airport. Just a normal grass field.

Not just helicopters. It happens all the time in my neck of the woods (Alaska) in small planes with big bouncy tires. We probably have more "field landings" (called bush landings, or "off airport operations") than landings at actual airports. OK, well maybe not quite that many - but enough that my local aviation college has an entire semester course dedicated to it for it's professional piloting program.
The first act is usually a low pass to inspect the conditions and determine the best landing direction (if there is more than one option), assuming that the winds will allow it. If there are other aircraft in the area, which sometimes happens at popular hunting/fishing/floating drop-off locations or glacier tours, then self-announcing on frequency is done like at a non-towered airport.  But, it's usually remote enough that it's not done.
Quite frequently, it's two planes for one party's charter - one to carry the people, and one to carry their gear. In that case, they're usually talking to each other the whole way, and know each other's intentions anyway.

Even in non-Alaskan parts of the country, such as Idaho & Nevada, there are a number airports which seem to differ from fields only in being marked on a sectional.  The low pass is to scare deer and/or cows off the runway.

+1 for @jamesqf. I learned to fly at a 1900x25 rural airport with a cow field next door. I didn't like flying at night there because the cows would often break through their fence and graze near or on the runway. We used to do an initial low pass over the runway to scare off the livestock that you could pretty much only see by their eyes. There were a couple of nights where I had to make a couple of passes before they moved. Cows aren't bright. :-/

@Shawn: One of my unfondest memories is of having just gotten wheels on the ground at Cedarville (extreme NE California) when a herd of deer ran across the runway.

@jamesqf In Louisiana, we also had big turtles that would sun themselves on the runway in the summer. Those things aren't much fun either.

@Shawn: Yeah, and I imagine it's not easy to scare them off the runway.  Even if you could, you'd probably run out of fuel waiting for them to get out of the way :-)

One thing to keep in mind when landing on any non-airport grass field: there's a fair chance that you won't notice the small rut in the grass until your nose wheel hits it. That's another reason why it's a good idea to do a low and slow pass over your intended landing area. Another thing to remember is that it's a lot easier to get in than it is to get out. You'd hate to make an awesomely successful landing in a field only to find out that you'll hit the trees at the far end on your way out.

I'm curious as to why the down-vote. Unless you've walked the field that you're planning to land in, even if it's maintained, there could be some geographical (or as I stated above, biological) obstacles that can impact your aircraft. And unless you're flying a VTOL aircraft, your takeoff distance will pretty much always be longer than your landing distance, ESPECIALLY in grass.

First of all, I look for power or telephone lines. The wires are almost invisible against the ground, but poles and towers are more or less conspicuous. Second, the wind has to be right, and third, the surface should be OK. Grass may seem nice, but it can disguise important irregularities, like irrigation ditches. The best is naked dirt, easy to examine by making a low pass...


text:
Why is it runway "1" instead of "01" in America?
In the case of a runway with a magnetic heading of 10° in America the runway number ("1") isn't hugely distinguishable from the runway centreline IMHO, (for example see Washington Airport and San Francisco Airport).
Is there a reason why the USA doesn't add the leading zero like the EU (example Brussels Airport and RAF Waddington)?
Does the ICAO make any recommendations about this?


text:
Can I shoot any approach at an uncontrolled airport in VMC without any clearance?
I am in IFR Flight plan to an uncontrolled airport. I find out that the weather is well above VFR limit, and hence canceled IFR flight plan. But I want to shoot an approach (with safety pilot) for my currency. In this case, can I still shoot any approach to the uncontrolled airport in VMC without any clearance?

These are two different questions.

For the first, your destination airport is above VFR, so you are planning to do an approach on the same airport as VFR after cancelling the flight plan, or a different airport?

Which country/regulations are you asking about? If you're asking about the US, your first question is answered here; your second one is answered here.

You would have to cancel your IFR flight plan with ATC, fly the duration of the flight and the approach by VFR, but, yes, you could.
Many people fly practice approaches at untowered airports by announcing their intentions over the CTAF.  This can be difficult to do at beehive airports with a lot of GA traffic going into and out of them, but it’s possible.  I’ve done it plenty of time without incident.

Flying VFR, of course. I would advise against it at a busy uncontrolled field though.